Self-inflating microcapsules

Abstract

A method comprises providing an aqueous solution having an alkaline pH and providing an oil including at least one silsesquioxane compound. The oil is added to the aqueous solution. The oil forms a plurality of silsesquioxane oil droplets suspended in the aqueous solution such that an internal osmotic pressure is generated inside the oil droplets via a chemical reaction. The aqueous solution is allowed to osmotically diffuse into the plurality of oil droplets for a predetermined time. The silsesquioxane oil droplets are polymerized by cross-linking the at least one silsesquioxane compound included in the silsesquioxane oil droplets to form a plurality of solidified microcapsules containing the aqueous solution therewithin.

What is claimed is: 
     
       1. A method, comprising:
 providing an aqueous solution having an alkaline pH; 
 providing an oil including at least one silsesquioxane compound; 
 adding the oil to the aqueous solution, the oil forming a plurality of silsesquioxane oil droplets suspended in the aqueous solution, the adding generating an internal osmotic pressure inside the oil droplets by means of a chemical reaction; 
 allowing the aqueous solution to osmotically diffuse into the plurality of silsesquioxane oil droplets for a predetermined time; and 
 polymerizing the silsesquioxane oil droplets by cross-linking the at least one silsesquioxane compound included in the silsesquioxane oil droplets to form a plurality of hollow microcapsules containing the aqueous solution therewithin; 
 removing the plurality of hollow microcapsules from the aqueous solution; 
 heating the plurality of hollow microcapsules to a temperature in a range of 50 degrees Celsius to 100 degrees Celsius to promote polymerization; 
 calcinating the plurality of hollow microcapsules at a temperature in a range of 200 degrees Celsius to 700 degrees Celsius; and 
 refilling the plurality of hollow microcapsules with the aqueous solution. 
 
     
     
       2. The method of  claim 1 , wherein the silsesquioxane compound includes at least one of a hydrolysable silane monomer and a low molecular weight silsesquioxane oligomer. 
     
     
       3. The method of  claim 2 , wherein the at least one silsesquioxane compound includes a compound of formula I:
   RSiO 3/2   (I)
 
 
       where:
 Si is silicon; 
 O is oxygen; and 
 R is hydrogen, alkyl, alkene, aryl or arylene. 
 
     
     
       4. The method of  claim 1 , wherein allowing the aqueous solution to osmotically diffuse into the oil droplets inflates the oil droplets. 
     
     
       5. The method of  claim 1 , wherein the chemical reaction includes a base catalyzed hydrolysis. 
     
     
       6. The method of  claim 1 , further comprising:
 dissolving a compound in the aqueous solution, 
 wherein the diffusing urges the compound to also diffuse into the oil droplets such that the plurality of hollow microcapsules contain the compound therewithin with the aqueous solution. 
 
     
     
       7. The method of  claim 6 , wherein the compound includes at least one of a fluorescent dye, a pharmaceutical, a nutraceutical, and a polymerizable moiety. 
     
     
       8. The method of  claim 1 , wherein the plurality of hollow microcapsules have a diameter in the range of 100 nm to 10 microns. 
     
     
       9. The method of  claim 1 , further comprising:
 dissolving a compound into the oil, 
 wherein a combination of the diffusing and polymerization separates the compound from the oil such that the plurality of hollow microcapsules contain the compound with the aqueous solution contained therewithin. 
 
     
     
       10. The method of  claim 1 , further comprising:
 suspending nanoparticles in the oil, 
 wherein the polymerization traps the nanoparticles into a shell of the plurality of hollow microcapsules. 
 
     
     
       11. The method of  claim 1 , further comprising:
 before refilling the plurality of hollow microcapsules with the aqueous solution, freezing the plurality of hollow microcapsules by:
 adding a surfactant to a solution containing the plurality of hollow microcapsules, and 
 adding an acid to the solution to reduce a pH of the plurality of hollow microcapsules to an acidic pH; and 
 adding a base to the solution after a time period to unfreeze the plurality of hollow microcapsules.